Down-link transmission inter-cell scheduling in CDMA data networks

• US 6,603,753 B1
• Filed: 12/03/1999
• Issued: 08/05/2003
• Est. Priority Date: 12/03/1999
• Status: Expired due to Fees

• Current Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Borst, Simon C., Bedekar, Anand S., Whiting, Philip A., Ramanan, Kavita, Yeh, Edmund M.
• Primary Examiner(s): Le, Thanh Cong
• Assistant Examiner(s): D'Agosta, Stephen
• Application Number:
  US09/454,040
• Time in Patent Office: 1,341 Days
• Field of Search: 455/450-453, 455/509, 455/511, 455/515, 455/516, 455/522, 455/523, 455/552, 455/553, 370/229-235, 370/318, 370/319-324, 370/326, 370/329-339, 370/341-345, 370/353
• US Class Current: 370/335
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 13/16 Code allocation
• CPC Class Codes: H04W 72/0446 Resources in time domain, e.g. slots or frames
• CPC Class Codes: H04W 72/541 using the level of interference
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A base station of a code division, multiple access (CDMA) telecommunications system employs scheduling of data transmission signals to corresponding user transceivers in down-link channels of a data network. One or more user transceivers may be in communication with a base station within a cell, and each user may have a minimum data rate requirement. In accordance with the present invention, the scheduling of user data transmission follows the constraints that 1) each base station transmits to user transceivers one at a time, and 2) the base station uses full available power for the down-link channel when transmitting (for data networks only). Given a data network of users, the method of scheduling and data rates may be modeled in accordance with a linear programming problem optimized according to a predefined criterion. In addition, the present method may be employed in a hybrid CDMA/time-share system to reduce power of data channels in communication with user transceivers near the base station. A continuum of rates may be achieved based on the system signal to interference ratio (S/I). The error rate requirement of a user'"'"'s down-link channel may be met provided the S/I of the channel is greater than a predetermined threshold value.

Claims

1. A method of allocating a transmission time interval to a corresponding user, for transmission of a spread data signal to the user by a given base station of a given cell in a network of cells, the method comprising:

a) defining a set of interference patterns for the given cell related to signal transmission characteristics between the corresponding user and one or more base stations of the network of cells, each cell of the network of cells having users and a base station capable of transmitting one or more spread data signals to such users,

wherein the signal transmission characteristics between the user and one or more base stations of the network of cells are one or more of a path loss gain, a signal-to-interference noise threshold, a transmission spectrum, and an orthogonality factor;

b) solving, in accordance with an optimizing criterion, a linear programming problem defined by (i) the set of interference patterns and (ii) a set of constraints for allocated time intervals based on the set of interference patterns, thereby to determine the time interval to be allocated; and

(c) responsive to the solution of the linear programming problem, allocating a recurrent time interval for the given base station to transmit therewithin spread data signals to the corresponding user, such that the recurrent time interval overlaps no time interval allocated to any other individual user belonging to the given cell.

2. The invention as recited in claim 1, wherein a recurrent time interval for base station transmissions is allocated to each of a group of two or more users belonging to the given cell, and the invention further comprises:

(d) transmitting at least one spread data signal, at a transmit power, from the given base station to each user of said group, such that the given base station transmits to only one member of the group at a time.

3. The invention as recited in claim 2, wherein for step (d) the transmit power is near a relative maximum transmit power of the base station.

4. The invention as recited in claim 2, wherein step (d) further includes the step of transmitting, by the base station, one or more spread signals to one or more corresponding delay-intolerant users in the cell.

5. The invention as recited in claim 4, wherein the base station transmits each spread signal of a delay-intolerant user during a corresponding time period that overlaps one or more allocated time intervals.

6. The invention as recited in claim 4, wherein each spread signal of a delay-intolerant user is either a voice or a voiceband data spread signal.

7. The invention as recited in claim 4, wherein, for step (d), the transmit power allocated to each spread data signal is the difference between a relative maximum transmit power of the base station and a total transmit power allocated to the one or more delay-intolerant spread signals;

and step (e) further includes the step of transmitting each spread data signal with the corresponding transmit power during the time interval.

8. The invention as recited in claim 2, wherein the time intervals and transmit powers of the one or more spread data signals are determined using received signal-to-interference noise values measured by corresponding users in the cell.

9. The invention as recited in claim 1, wherein each interference pattern corresponds to a combination of thermal noise power and interference noise power of spread data signals from cells of the network of cells.

10. The invention as recited in claim 9, wherein the network of cells is a linear network, and the set of interference patterns for the cell are defined by the combinations generated by two adjacent cells.

11. The invention as recited in claim 1, wherein, for step (c), each user of a first set of users is allocated to a corresponding one of a set of disjoint time intervals, and each user of a second set of users is allocated to a common time interval.

12. The invention as recited in claim 11, wherein, for step (c), the corresponding spread user signals for the second set of users are transmitted concurrently during the common time interval.

13. The invention as recited in claim 11, wherein each user is assigned to either the first or second set of users based on a set of spreading constraints.

14. The invention as recited in claim 1, wherein, for step (b) the optimization criterion is each user achieves a relatively maximum average throughput given a relative minimum average throughput for each user in the cell.

15. A base station of a cell in a network of cells, the base station including apparatus for allocating a transmission time interval to a corresponding user, for transmission of a spread data signal to the user by a given base station of a given cell, the apparatus comprising:

measuring module that determines a set of interference patterns for the given cell related to signal transmission characteristics between the corresponding user and one or more base stations of the network of cells, each cell of the network of cells having users and a base station capable of transmitting one or more spread data signals to such users,

wherein the signal transmission characteristics between the user and one or more base stations of the network of cells are one or more of a path loss gain, a signal-to-interference noise threshold, a transmission spectrum, and an orthogonality factor; and

a processing module comprising

a first sub-module that solves, in accordance with an optimizing criterion, a linear programming problem defined by (i) the set of interference patterns and (ii) a set of constraints for allocated time intervals based on the set of interference patterns, thereby to determine the time interval to be allocated; and

a second sub-module that, responsive to the solution of the linear programming problem, allocates a recurrent time interval for the given base station to transmit therewithin spread data signals to the corresponding user, such that the recurrent time interval overlaps no time interval allocated to any other individual user belonging to the given cell.

16. The invention as recited in claim 15, wherein a recurrent time interval for base station transmissions is allocated to each of a group of two or more users belonging to the given cell, and the invention further comprises:

a transmit module that transmits at least one spread data signal, at a transmit power, from the given base station to each user of said group, such that the given base station transmits to only one member of the group at a time.

17. The invention as recited in claim 16, wherein the transmit power is near a relative maximum transmit power of the base station.

18. The invention as recited in claim 16, wherein the transmitter transmits one or more spread signals to one or more corresponding delay-intolerant users in the cell.

19. The invention as recited in claim 18, wherein the base station transmits each spread signal of a corresponding delay-intolerant user during a corresponding time period that overlaps one or more time intervals.

20. The invention as recited in claim 18, wherein each spread signal of a delay-intolerant user is either a voice or a voiceband data spread signal.

21. The invention as recited in claim 18, wherein the transmit power allocated to each spread data signal is the difference between a relative maximum transmit power of the base station and a total transmit power allocated to the one or more delay-intolerant spread signals;

and step (e) further includes the step of transmitting each spread data signal with the corresponding transmit power during the time interval.

22. The invention as recited in claim 16, wherein the time intervals and transmit powers of the one or more spread data signals are determined using received signal-to-interference noise values measured by corresponding users in the cell.

23. The invention as recited in claim 15, wherein each interference pattern corresponds to a combination of thermal noise power and interference noise power of spread data signals from cells of the network of cells.

24. The invention as recited in claim 23, wherein the network of cells is a linear network, and the set of interference patterns for the cell are defined by the combinations generated by two adjacent cells.

25. The invention as recited in claim 15, wherein each user of a first set of users is allocated to a corresponding one of a set of disjoint time intervals, and each user of a second set of users is allocated to a common time interval.

26. The invention as recited in claim 25, wherein the corresponding spread user signals for the second set of users are transmitted concurrently during the common time interval.

27. The invention as recited in claim 25, wherein each user is assigned to either the first or second set of users based on a set of spreading constraints.

28. The invention as recited in claim 15, wherein, for step (c) the optimization criterion is each user achieves a relatively maximum average throughput given a relative minimum average throughput for each user in the cell.

29. A computer-readable medium having stored thereon a plurality of instructions, the plurality of instructions including instructions which, when executed by a processor, cause the processor to implement a method of allocating a transmission time interval to a corresponding user, for transmission of a spread data signal to the user by a given base station of a given cell in a network of cells, the method comprising the steps of:

a) defining a set of interference patterns for the given cell related to signal transmission characteristics between the corresponding user and one or more base stations of the network of cells, each cell of the network of cells having users and a base station capable of transmitting one or more spread data signals to such users,

wherein the signal transmission characteristics between the user and one or more base stations of the network of cells are one or more of a path loss gain, a signal-to-interference noise threshold, a transmission spectrum, and an orthogonality factor;

b) solving, in accordance with an optimizing criterion, a linear programming problem defined by (i) the set of interference patterns and (ii) a set of constraints for allocated time intervals based on the set of interference patterns, thereby to determine the time interval to be allocated; and

c) responsive to the solution of the linear programming problem, allocating a recurrent time interval for the given base station to transmit therewithin spread data signals to the corresponding user, such that the recurrent time interval overlaps no time interval allocated to any other individual user belonging to the given cell.